Hill Audio documentation - anyone to contribute?

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Hi all,

I own a couple of legacy Hill Audio products (Multimix, Datum, LC1200) and found it quite hard to find documents such as manuals, schematics, old brochures, pictures etc. I would like to make it easier for all those guys who own equipment of this brand and I want to put a simple website together with all documents I already found and those i can find. After all, this stuff is worth maintaining it or even customozing it (really love the Multimix).

If anyone has any Hill Audio documents to contribute, please do me and other guys out there a favor and send it to me (grooverider68@yahoo.com) ....I'll put it together and will announce the website once ready. Best would be pdf or jpg.

Thanks to all of you!

Hi I am new to this but wonder if anyone can help I have a Hill Audio LC1200 power amp with a strange fault Loud Buzzing noise from both speakers if I disconnect the HT from one channels (does.t matter which) the other channel then works fine !!. Did you manage to get a schematic I would be most grateful if you could let me have a scan/pdf of it. Any help will be much appreciated.

I feel terrible. I was the test dept. manager at Hill audio for a number of years and worked on all their amps & mixing desks. I feel terrible because I used to have all the schematics but binned them.

The main fault I found on the LC amp range was around the fan driver. There's a modification under the PCB around the heatsink of the device that feeds the DC cooling fans. If the fans stop working or you get buzzing on both channels I suggest you replace the electrolytic capacitor UNDER the pcb and a tantalum capacitor on the top side (I think it's on the top, might not be). Also, if memory serves, there's a zenner diode. Check that too.

As far as Hill's mixing desks are concerned, they are really quite simple. If you get a problem on a single module it's probably either a dodgy potentiometer, a connection problem (check soldering as well as cable connectors) or a blown 5532 op amp.

My guilt is slightly eased.
hi jooolsb
so you should feel terrible, chucking that stuff away, have a slap on the wrist.

i have worked on loads of hills amps over the years, i have a couple of customers that love em, especially the LC1200. they tell me that the bass is rounded and pleasant.

i used up all the spares i had in stock for these beasts.

i do have some information on the LC series and a very poor diagram of DX amp.

i concure with the capacitor on the fan control circuit giving trouble, this is because it was right next to heat sink and dried out causing buzzing on both channels, replace with 105 deg type and leave legs long so you can mount away from heasink.
also i found that the zobel capacitors were failing this was corrected with a good quality part.

now off to scan the info if any one wants it.
oh dear, i have mislaid the bulk of my Hill Audio stuff cant find it anywhere at the moment. should i slap myself on the wrist? :xeye:

however here are the drawings (such as they are) that i have found. one is the driver/front board the other is the back board, the one missing is the output board.

i do have a full set for the LC Series in a folder that has dissapered i will post when i find it


  • rear board.pdf
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Well done Bob.
Note: Rear board schematic doesn't include the fan modification.

The sound of all the LC's is beautiful. Tha bass is amazing. The main difference between the 400, 800 and 1200 is the transformer and the number of output devices.

I did read something on another site where someone had replaced the DC fans with constantly operating mains AC fans. Good idea if the noise isn't an issue.

I agree about the DX schematic being bad - never did find a good one!
No idea about replacement output transistors I'm afraid. To make matters worse, the originals all had their gain tested to make sure only tranisistors with the same gain were used on each heatsink.

I think the implications of having different ones was an increased DC offset.
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